In vivo analysis of Argos structure-function. Sequence requirements for inhibition of the Drosophila epidermal growth factor receptor.
The Drosophila Argos protein is the only known extracellular inhibitor of the epidermal growth factor receptor (EGFR). It is structurally related to the activating ligands, in that it is a secreted protein with a single epidermal growth factor (EGF) domain. To understand the mechanism of Argos inhibition, we have investigated which regions of the protein are essential. A series of deletions were made and tested in vivo; furthermore, by analyzing chimeric proteins between Argos and the activating ligand, Spitz (a transforming growth factor-alpha-like factor), we have examined what makes one inhibitory and the other activating. Our results reveal that Argos has structural requirements that differ from all known EGFR activating ligands; domains flanking the EGF domain are essential for its function. We have also defined the important regions of the atypical Argos EGF domain. The extended B-loop is necessary, whereas the C-loop can be replaced with the equivalent Spitz region without substantially affecting Argos function. Comparison of the argos genes from Drosophila melanogaster and the housefly, Musca domestica, supports our structure-function analysis. These studies are a prerequisite for understanding how Argos inhibits the Drosophila EGFR and provide a basis for designing mammalian EGFR inhibitors.
Howes
R
R
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
Wasserman
J D
JD
Freeman
M
M
D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000737:chemistry* / Q000196:embryology; D004815:Epidermal Growth Factor; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D005123:Eye / Q000254:growth & development / Q000648:ultrastructure; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D006793:Houseflies / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D013329:Structure-Activity Relationship; D014921:Wings, Animal / Q000254:growth & development
D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C075638:aos protein, Drosophila; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor; D066246:ErbB Receptors